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  • SR power potential

    Back when I originally bought my 240sx I read that sr20det will do up to 400 whp on stock block. And I think this is why I continue to keep the car, the "400 whp" that I can have.

    Doing some NASA ST calculations for 2650 comp weight:

    ST3: 301/315 whp depending on tires
    ST2: 340/358 whp depending on tires

    315 whp for ST3 on small tire looks to be a good bit under the "400 whp" cap.

    My question is, I want to run the car for up to 2 hours/day 50 days per year and have the engine last a few years (Miata made it to 4). Will stock internals still hold at this level of use? If not, what is the max power that I can expect to stay together?
    winhpde.com

  • #2
    Reliable fuel, good tune, proper heat management, and quality parts should be no issue at those power levels.

    A good friend of mine beat the hell out of his doing drift events at probably 280whp or so for around 8 years or so. He drove it to events in Houston, Mineral Wells, and Stroud, drifted all day, and drove it back. The last compression test dropped to around 135-140psi on all 4 cylinders so he is tossing in fresh rings and bearings before tracking it again.

    He kept a mileage log and has around 100,000 miles on it in addition to what was put on it in Japan. His primary trick was addressing any little issues like vacuum leaks as they came up and performed regular maintenance. We averaged 31mpg the last time we drove it back from Mineral Wells.

    I wouldn't expect 30-40whp to be much different following the recipe above.

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    • #3
      how much tire are you looking at for those power levels?
      300whp and 2650lbs will need minimum of a 255 R-comp to last a 30 minute race.
      Originally posted by SoSideways
      I don't care what color they are as long as they are LONG AND HARD.
      '04 G35 Sedan 6MT- The DD
      '96 240SX- The Track Toy

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      • #4
        I wouldn't think you would have any problems at those power levels as long as everything is properly managed, cooling and fueling being your biggest issues. A safe tune and sub 200F coolant temps should keep the motor quite happy.

        The saving grace is that you don't need to turn 8000rpm to make that power so you won't really be stressing the rotating assembly or valvetrain stability.
        I am SKULLWORKS

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        • #5
          Yea, it should easily handle that power, and like Mike says, don't turn it to the moon and the valvetrain will be reliable.

          If you run it on E85 it'll easily do that much power all day long with no troubles, but with E10 you're going to need lots of cooling and to have a safe tune.

          The other issue is if you chase super high midrange torque to max out the rules - you WILL make the thing a ticking time bomb. Over about 19-20 psi detonation is always lurking as things heat up. So keep in mind a 300 rwhp powerband may not be very strong in the midrange if you're just running something like 12 psi on a GT2871R with some mild cams (which will easily belt out 300 rwhp, but maybe like 230-250 rwtq).
          '18 Chevrolet Volt - Electric fun hatch for DD duty!


          DefSport Koni Sleeve and Spring Perch Buy!!!
          http://www.nissanroadracing.com/showthread.php?t=5902

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          • #6
            Keep in mind more power isn't always better if you can't put that power down. More traction means more corner speeds which means higher exit speed which leads to high strait away speeds. 300whp and 255 or 275 tires is a great combo in these cars, no real need for more if you can carry a lot of corner speed.

            Cams will raise your TQ to redline which adds a ton of acceleration midrange to redline.

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            • #7
              So 300 whp and a 275 tire is the ticket?

              Getting an ST*-friendly powerband seems tricky. I want a bigger turbo to make more power then level off the top end, but a bigger turbo moves the power into the top end? Any turbo recommendations? I am going to feed it 93 octane, no E85 here and I certainly don't have pockets for race gas.
              winhpde.com

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              • #8
                255/40-17 is the hot ticket.

                A GT2560R/aka S14/S15 T28 would do it turned up greatly, but a 0.64 A/R GT2871R would do it no problem. Taper the boost down with cams to keep it at 300 rwhp-ish.


                An EFR6258 would do it with better low end response, but probably wouldn't affect things too much on track.
                '18 Chevrolet Volt - Electric fun hatch for DD duty!


                DefSport Koni Sleeve and Spring Perch Buy!!!
                http://www.nissanroadracing.com/showthread.php?t=5902

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                • #9
                  There is no "power limit".
                  Stock SR20 pistons have weak ringlands. They absolutely can't take det, and i mean it; do not settle for the odd det or so like most engine managements go. NO det at all, or kiss your ringlands goodbye. As long as you can contain det, you are safe.
                  This is solved by using e85 fuel, or high octane and forged pistons with beefier ringlands. On 93 octane, safe power will be hard.

                  Turbo wise, i'd say second hand gt2871r for cheap, or new gtx2867r for newer tech and more power room. but really, you want forged pistons.

                  You might get boost creep from a gt2871r .64 so take the bigger version if you can. The gtx series will net you 400+ (and will still spool faster than a 2871). I posted the vid of an SR20 with a high end gtx2867r setup some time ago, if you want to see what gives. It is a high end setup with a forged engine and e85 though.

                  The second biggest SR20 killer (self taught mechanics and dreamers aside) is the cam oil spraybars that clog and ruin the whole engine, starting with camshafts. This happens with any kind of power. I recommend cleaning them once in a while.

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                  • #10
                    Stock SR20 pistons aren't THAT weak. Sure, if you're banging on them at 400 rwhp with constant DET, you're going to trash any sort of cast piston with that sort of abuse. But a little phantom knock here and there isn't going to kill them. When I was dyno tuning stock ROMs, guys would always ask me to push it to that point for the "sweet dyno graph number." In fact, I've seen quite a few JWT/Enthalpy cars that had some pretty damn aggressive timing maps and were operating on phantom knock or over for quite a while with not much ill happening except for lots of aluminum specks on the spark plugs (once I showed it to them they would always freak out a bit).

                    GT2871R 0.64 A/R won't creep at about 11-12 psi, especially if you slightly port the WG hole (good idea if you're thinking of running boost on the lower side). GTX2867R really hasn't been posting up any higher power numbers any the GT2871R. I can get them and save you guys a little cash new, but I'm not sure it's worth it from what I've seen on the interwebs.


                    Oil sprayers clogging is a big one. Check on a new engine that they are clear. But changing oil often never gave me any issues there. The o-ring popping at the oil pump to block seal is a bad one - it's what did my SR in near as I can tell (just sold the block, didn't tear it down).

                    Some people toss rockers if their head isn't shimmed well, or smashing against the rev limiter repeatedly. But I don't think it's as common as internet lore would lead one to believe, and more down to abuse/stupidness. You can do the dual guide shim mod as well if you want to spend the time.


                    But I would go with some mild cams like 256/256 Tomeis or something like that, then maybe not be so dead set of 400 rwhp if you get a GT2871R, because it might tap out around 370-380 rwhp or so if you're on E10 and don't want to push it to high heaven.
                    '18 Chevrolet Volt - Electric fun hatch for DD duty!


                    DefSport Koni Sleeve and Spring Perch Buy!!!
                    http://www.nissanroadracing.com/showthread.php?t=5902

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                    • #11
                      Never heard of the cam oil spray bar issue, good to know. Here is a howto for my future reference: http://www.sxoc.com/vbb/showthread.p...48#post3096648

                      And this: http://www.sr20-forum.com/informatio...pray-bars.html

                      Def, did I read you correctly that a GTX turbo offers no benefit over a GT?
                      winhpde.com

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                      • #12
                        Who said that? If you're talking about what I said, I was talking about the GTX2867 doesn't make more power than a GT2871 on our engines. But in betting the transient response on the GTX is better.

                        Some GTX turbos do better than their GT counterparts, others offer almost no difference from a power perspective.
                        '18 Chevrolet Volt - Electric fun hatch for DD duty!


                        DefSport Koni Sleeve and Spring Perch Buy!!!
                        http://www.nissanroadracing.com/showthread.php?t=5902

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                        • #13
                          Right, that is what I thought.
                          winhpde.com

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                          • #14
                            I had a S15 turbo (GT28R) and went to a GTX2867R. At 15 PSI the GTX made 50 more horsepower than the S15 turbo on the same dyno, same engine. I did add larger injectors and had enthalpy send out a new tune due to different turbo and injectors.

                            The spool seems a little slower like 200rpm but it made more power everywhere even down low so not an issue. The GTX power delivery feels more linear. The S15 would feel like nothing, then everything.
                            Chicago Region SCCA SM # 688 http://www.scca-chicago.com
                            TSSCC SM # 688 http://www.tsscc.org

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                            • #15
                              Originally posted by eye-5 View Post
                              The GTX power delivery feels more linear. The S15 would feel like nothing, then everything.
                              For a race car, this is the most important part. ****loads of power don't do you any good if you spin the car every time you get into boost on corner exit.

                              It's a little different on a time attack car where you typically have a little more room on track. But if you're wheel 2 wheel with someone or trying to set up a pass on corner exit (or trying to outrun someone behind you), the LAST thing you want to do is kick the car sideways and have to recover before you really start going anywhere.

                              I've won several races locally against some 300+WHP Solstices because the power is so peaky on them they're almost undriveable.
                              Originally posted by SoSideways
                              I don't care what color they are as long as they are LONG AND HARD.
                              '04 G35 Sedan 6MT- The DD
                              '96 240SX- The Track Toy

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